Electric vehicle charging device and method for charging electric vehicle

ABSTRACT

An electric vehicle charging device includes a processing unit having a memory with a routine stored therein which, when executed by the processing unit causes the processing unit to control circuitry to prevent the electric vehicle charging device from charging an electric vehicle for a random delay period and to allow the electric vehicle charging device to charge the electric vehicle starting when the random delay period ends, wherein the random delay period starts at a predetermined start time and lasts a random delay length of time. The random delay reduces the peak load on a transformer that the electric vehicle charging device and other electric vehicle charging devices receive power from.

BACKGROUND Field

The disclosed concept relates generally to electric vehicles, and moreparticularly, to electric vehicle charging devices. The disclosedconcept also relates to methods for charging electric vehicles.

Background Information

An electric vehicle (EV) periodically needs to be plugged in to rechargeits battery. An EV is often plugged in to recharge at the owner'sresidence. Recharging an EV, however, requires a significant amount ofpower.

In many types of residential power distribution systems a transformerreceives power from a utility. Power is then provided from thetransformer to multiple residences via power lines between thetransformer and load centers of the residences. For example, onetransformer may service an entire neighborhood. There is a limit to theamount of power that can pass through the transformer and if theresidences serviced by the transformer attempt to draw too much powersimultaneously, the transformer can become overloaded.

As EVs become more common and more EVs are charged at residences, thepower requirements for a set of residences serviced by a transformer cansignificantly increase due to the power required to charge the EVs. Theincrease can create a situation where a transformer becomes overloadedand cannot meet the power demands of the residences it services duringpeak demand times. Replacing the transformer with a higher capacitytransformer or adding additional transformers so that each transformerservices a lower number of residences would solve the problem. However,these solutions are very expensive. It is desirable to cope with theincreased power requirements of residences due to EV charging in a lesscostly manner.

There is room for improvement in electric vehicle charging devices.There is also room for improvement in methods for charging electricvehicles.

SUMMARY

These needs and others are met by embodiments of the disclosed concept,which are directed to an electric vehicle charging device capable ofreducing the peak load imposed on a transformer due to charging ofmultiple electric vehicles. These needs and others are also met byembodiments of the disclosed concept, which are directed to a method ofcharging an electric vehicle which reduces the peak load imposed on atransformer due to charging of multiple electric vehicles.

In accordance with aspects of the disclosed concept, an electric vehiclecharging device for use in charging a corresponding electric vehicleelectrically connected to the electric vehicle charging devicecomprises: control circuitry structured to selectively allow theelectric vehicle charging device to charge the electric vehicle; aprocessing unit having a memory with a routine stored therein which,when executed by the processing unit causes the processing unit to:estimate a charging length of time needed for the electric vehicle toreach a fully charged state; determine a maximum delay length of time asa difference between a predetermined length of time and the charginglength of time, wherein the predetermined length of time is defined by apredetermined start time and a predetermined end time; randomly select arandom delay length of time that is less than or equal to the maximumdelay length of time; and control the control circuitry to prevent theelectric vehicle charging device from charging the electric vehicle fora random delay period and to allow the electric vehicle charging deviceto charge the electric vehicle starting when the random delay periodends, wherein the random delay period starts at the predetermined starttime and lasts the random delay length of time.

In accordance with other aspects of the disclosed concept, an electricvehicle charging device for use in charging a corresponding electricvehicle electrically connected to the electric vehicle charging devicecomprises: control circuitry structured to selectively allow theelectric vehicle charging device to charge the electric vehicle; acommunication interface structured to provide communication with otherelectric vehicle charging devices; a processing unit having a memorywith a routine stored therein which, when executed by the processingunit causes the processing unit to: initiate a load shedding processhaving an associated load shedding power level and a load sheddingperiod of time; estimate a charging length of time needed for theelectric vehicle to reach a fully charged state; control thecommunication interface to transmit the charging length of time to oneor more other electric vehicle charging devices associated with otherelectric vehicles; receive charging length of times associated withother electric vehicles via the communication interface; determinecharging priority ranks of the electric vehicle and the other electricvehicles based on the charging lengths of time associated with theelectric vehicle and the other electric vehicles; determine a thresholdrank based on the load shedding power level; and control the controlcircuitry to prevent the electric vehicle charging device from chargingthe electric vehicle for the load shedding period of time if thecharging priority rank of the electric vehicle is equal to or less thanthe threshold rank and to allow the electric vehicle charging device tocharge the electric vehicle for the load shedding period of time if thecharging priority rank of the electric vehicle is greater than thethreshold rank.

In accordance with other aspects of the disclosed concept, a method ofcharging an electric vehicle with an electric vehicle charging devicecomprises: estimating a charging length of time needed for the electricvehicle to reach a fully charged state; determining a maximum delaylength of time as a difference between a predetermined length of timeand the charging length of time, wherein the predetermined length oftime is defined by a predetermined start time and a predetermined endtime; randomly selecting a random delay length of time that is less thanor equal to the maximum delay length of time; and preventing theelectric vehicle charging device from charging the electric vehicle fora random delay period and allowing the electric vehicle charging deviceto charge the electric vehicle starting when the random delay periodends, wherein the random delay period starts at the predetermined starttime and lasts the random delay length of time.

In accordance with other aspects of the disclosed concept, a method ofcharging an electric vehicle with an electric vehicle charging devicecomprises: initiate a load shedding process having an associated loadshedding power level and a load shedding period of time; estimating acharging length of time needed for the electric vehicle to reach a fullycharged state; transmitting the charging length of time to one or moreother electric vehicle charging devices associated with other electricvehicles; receiving charging length of times associated with otherelectric vehicles; determining charging priority ranks of the electricvehicle and the other electric vehicles based on the charging lengths oftime associated with the electric vehicle and the other electricvehicles; determining a threshold rank based on the load shedding powerlevel; and preventing the electric vehicle charging device from chargingthe electric vehicle for the load shedding period of time if thecharging priority rank of the electric vehicle is equal to or less thanthe threshold rank and allowing the electric vehicle charging device tocharge the electric vehicle for the load shedding period of time if thecharging priority rank of the electric vehicle is greater than thethreshold rank.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an electrical distribution system inaccordance with an example embodiment of the disclosed concept;

FIG. 2 is a schematic diagram of an electric vehicle charging circuitbreaker in accordance with an example embodiment of the disclosedconcept;

FIG. 3 is a flowchart of a constrained random delay method of chargingan electric vehicle in accordance with an example embodiment of thedisclosed concept;

FIG. 4 is a chart illustrating a result of implementing the method ofFIG. 3;

FIG. 5 is a chart illustrating the result of implementing apredetermined delay time method of charging an electric vehicle;

FIG. 6 is a flowchart of a load shedding algorithm in accordance with anexample embodiment of the disclosed concept; and

FIG. 7 is a chart illustrating a result of an implementation of the loadshedding algorithm of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein.

As employed herein, the term “processor” shall mean a programmableanalog and/or digital device that can store, retrieve and process data;a controller; a control circuit; a computer; a workstation; a personalcomputer; a microprocessor; a microcontroller; a microcomputer; acentral processing unit; a mainframe computer; a mini-computer; aserver; a networked processor; or any suitable processing device orapparatus.

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

As employed herein, the term “electric vehicle” or “EV” shall mean avehicle that uses electric power to drive and refers to vehicles thatonly use electric power to drive or hybrid vehicles that, for example,use electric power, combustion power, or a combination thereof to drive.

For many EV owners, postponing the time that the EV starts charginguntil later in the night does not present any inconvenience. Forexample, in a typical scenario an EV owner returns from work in theevening and plugs in their EV to charge overnight. Often, the owner doesnot need the EV to charge for later use in the evening. Rather, in mostcases, as long as the EV is fully charged by the next morning, there isno inconvenience to the user.

The demand for electricity in residential areas historically peaks inthe evening hours and is very low late at night and very early in themorning. Adding EV charging to the already high demand in the eveningcan put a strain on the electrical distribution system servicing aresidential area. In particular, the demand for electricity can overloada transformer servicing a set of residences. In accordance with someexample embodiments of the disclosed concept, an electrical distributionsystem can coordinate the charging of EVs in order to minimize thedemand during peak load times. For example and without limitation, theelectrical distribution system may control EV charging so that it isdeferred to a lower demand time such as late at night or early in themorning.

Delaying the charging of EVs until after a defined peak load periodalone can cause another issue. Namely, if all of the EVs serviced by atransformer begin charging simultaneously after the end of the definedpeak period, the demand for electricity from the EVs simultaneouslycharging could potentially cause the transformer to overload. Staggeringthe charging of the EVs though the night can smooth the peak load causedby the EVs and reduce the risk of the transformer overloading. Inaccordance with some example embodiments of the disclosed concept,electric vehicle charging devices can charge EVs in a manner thatreduces the peak load caused by charging the EVs.

FIG. 1 is a schematic diagram of an electrical distribution system 1 inaccordance with an example embodiment of the disclosed concept. Theelectrical distribution system 1 includes a transformer 100 and one ormore load centers 200. The transformer 100 is configured to receivepower from a utility 10 and provide the received power to the loadcenters 200. In some example embodiments of the disclosed concept, theload centers 200 may each correspond to a residence. Each load center200 may provide power to one or more electrical devices at thecorresponding residence (e.g., without limitation, an EV 400, a heating,ventilation, and air conditions system (HVAC) 410, a water heater 420,etc.).

In an example embodiment of the disclosed concept, one or more of theload centers 200 includes one or more EV charging circuit breakers 300.In some embodiments, the EV charging circuit breakers 300 are circuitbreakers that are capable of providing a Level 2 AC EV chargingcapability. The EV charging circuit breakers 300 may work in conjunctionwith an EV charging station and/or an EV charging cable to charge acorresponding EV 400.

The EV charging circuit breakers 300 are able to generate EV charginginformation about their corresponding EVs 400. The EV charginginformation may include an estimated time to fully charge the EV 400 oran estimated time remaining for the EV 400 to reach a fully chargedstate. For example, the EV charging circuit breakers 300 may be able todetermine a time that the EV 400 was plugged in. The EV charging circuitbreakers 300 may also be able to estimate the state of charge of the EV400 (e.g., the percentage of charge the EV 400 has) and the total chargeenergy needed during a charge event by, for example, monitoringhistorical charge patterns of the EV 400 and the instantaneous powerdrawn by a charger in the EV 400. Chargers in EVs 400 are typicallycapable of drawing different amounts of power from an external chargingdevice such as the EV charging circuit breakers 300. When the state ofcharge of the EV 400 is low, the charger in the EV 400 will typicallydraw the highest amount of power it is rated for. As the state of chargeof the EV 400 increases to its maximum, the charger in the EV 400 willdraw a lower amount of power to maintain constant battery voltage. Thetime from when the EV 400 is plugged in to the time when the charger inthe EV 400 reduces the amount of power drawn is an estimate of theamount of time it takes to fully charge the EV 400. Metering circuitryincluded in the EV charging circuit breaker 300 may be used to monitorthe amount of power drawn by the charger in the EV 400 and, thus the EVcharging circuit breaker 300 may thus be able to determine the time whenthe EV 400 reaches the fully charged state (e.g., the time when thecharger in the EV 400 reduces the amount of power it draws. The EVcharging circuit breaker 300 is thus able to estimate the time it takesto fully charge the EV 400 as the time from when the EV 400 is pluggedin to when the EV 400 reaches its fully charged state withoutinterruptions in charging. When estimating the time to reach the fullycharged state, the EV charging circuit breaker 300 may subtract anyinterruptions in charging.

Each time the EV 400 is charged, the EV charging circuit breaker 300 maystore the amount of time taken to fully charge the EV 400 as historicalcharge pattern data. The historical charge pattern data allows the EVcharging circuit breaker 300 to more accurately estimate the time itwill take to fully charge the EV 400 when it is plugged in. For example,the historical charge pattern data may show that the time to fullycharge the EV 400 is correlated with the time the EV 400 was plugged in.For instance, the historical data may show that the EV 400 typicallytakes about 3 hours to fully charge when it is plugged in at 2:00 PM,but it typically takes about 6 hours to fully charge when it is pluggedin at 8:00 PM. Thus, if the EV 400 is plugged in at 8:00 PM, the EVcharging circuit breaker 300 may determine that the estimated time tofully charge the EV 400 is about 6 hours. While a correlation betweenthe historical time to fully charge and the plug-in time is one exampleof how the historical charge pattern data may be used to more accuratelyestimate the time to fully charge the EV 400, it will be appreciated bythose having ordinary skill in the art that there are a variety of waysthat the historical charge pattern data may be used to more accuratelyestimate the time to fully charge the EV 400. For example, recenthistorical charge pattern data may be weighted more heavily than oldercharge pattern data, a correlation between the time of year (e.g.,winter, summer, etc.) and the historical charge pattern data may beused, etc.

Once the EV charging circuit breaker 300 has estimated a time to fullycharge the EV 400, it EV charging circuit breaker 300 may estimate theremaining time to reach the fully charged state. The estimated timeneeded to reach the fully charged state is the estimated time to fullycharge the EV 400 minus the time that the EV 400 has been charging.Thus, if the estimated time to fully charge the EV 400 is 6 hours andthe EV 400 has been plugged in and charging for 2 hours, the time neededto reach the fully charged state is 4 hours. The EV 400 is able toestimate the time needed for the EV 400 to reach the fully charged statewithout directly communicating with the EV 400. However, it iscontemplated that in some embodiments, the EV charging circuit breaker300 may communicate with the EV 400 and use information from the EV 400to estimate the time needed for the EV 400 to reach the fully chargedstate.

The EV charging circuit breakers 300 and the transformer 100 may bothhave the capability of communicating. For example, the EV chargingcircuit breakers 300 and transformer 100 may be able to communicate witheach other or other devices via wired and/or wireless communication. Insome example embodiments of the disclosed concept, the EV chargingcircuit breakers 300 and/or the transformer 100 are able to communicatewirelessly using one or more suitable wireless communication protocols(e.g., Wi-Fi, Bluetooth®, radiofrequency, etc.). Additionally, in someexample embodiments of the disclosed concept, the EV charging circuitbreakers 300 and/or the transformer 100 are able to communicate via oneor more wired communication protocols. The EV charging circuit breakers300 and/or the transformer 100 may also be able to communicate with theutility 10 or other power sources such as a renewable power source(e.g., without limitation, a photovoltaic system 20).

In some example embodiments of the disclosed concept, the EV chargingcircuit breakers 300 are configured to control the charging of theircorresponding EVs 400 by delaying charging of the EVs 400 a randomamount of time after a predetermined peak load time. For example, a timeperiod for charging the EVs 400 may be the time between the end of thepredetermined peak load time (e.g., 10:00 PM) and a predetermined timein the morning (e.g., 6:00 AM). Each of the EV charging circuit breakers300 estimates the time required for their corresponding EVs 400 to reachthe fully charged state and determines the maximum amount of time thatcharging may be delayed after the end of the predetermined peak loadtime while still leaving enough time to charge the EV 400 to its fullycharged state by the predetermined time in the morning. The EV chargingcircuit breaker 400 then selects a random delay time less than or equalto the maximum amount of time the charging may be delayed. The EVcharging circuit breaker 300 then begins charging the EV 400 after therandom delay time.

Delaying charging until after the predetermined peak load time eases thepeak load on the transformer by preventing the EVs 400 from chargingduring the peak load time. Each EV charging circuit breaker 300 selectsits own random delay time so the EV charging circuit breakers 300 do notall start charging their corresponding EVs 400 simultaneously, thussmoothing the load applied to the transformer 100 by the EVs 400.

In some embodiments of the disclosed concept, the electricaldistribution system 1 may use a load shedding algorithm which may causeselected ones of the EV charging circuit breakers 300 to stop chargingtheir corresponding EVs 400 for a period of time. The load shedding mayhave an associated load shedding level and period of time. For exampleand without limitation, the load shedding level may be 100 kW and theassociated time period may be 9:00 PM-11:00 PM. However, it will beappreciated that any load shedding level and period of time may beselected without departing from the scope of the disclosed concept.During the load shedding period, the load shedding algorithm may causeselected ones of the EV charging circuit breakers 300 to stop chargingtheir corresponding EVs 400 for the period of time in order to reducethe load on the transformer 100 by the load shedding level. After theperiod of time, the EV charging circuit breakers 300 may resume chargingtheir corresponding EVs 400.

The load shedding algorithm may use EV charging information (e.g.,estimated time until the EV 400 reaches its fully charged state) to rankthe EVs 400 and determine which EV charging circuit breakers 300 tocontrol to stop charging. For example, the load shedding algorithm mayaim to have all EVs 400 fully charged by a predetermined time in themorning. If an EV 400 is very low on charge and would not be fullycharged by morning if its charging were turned off during the loadshedding period, the load shedding algorithm may rank that EV 400 as ahigh priority for charging during the load shedding period. Other EVs400 that do not require a significant amount of time to reach a fullycharged state may receive a lower priority rank for charging during theload shedding period. The load shedding algorithm may causing chargingto be turned off for the lowest rank EVs 400 until the load sheddinglevel is met. For example, if the load shedding level is 100 kW and eachEV 400 draws 10 kW for charging, the load shedding algorithm will causethe ten lowest ranked EVs 400 to stop charging.

In some example embodiments of the disclosed concept, the load sheddingalgorithm may have a set time period associated with load shedding. Forexample, the associated time period may be a predetermined time periodeach day. However, in some embodiments of the disclosed concept, thetime period associated with load shedding may be triggered by an event.For example, the transformer 100 may monitor its load and initiate loadshedding when its load reaches a predetermined level so as to preventthe transformer from overloading. The time period associated with loadshedding may have a fixed or variable length.

In some embodiments of the disclosed concept, the load sheddingalgorithm may be implemented by routines executed in the EV chargingcircuit breakers 300 and/or the transformer 100. The EV charging circuitbreakers 300 may communicate the EV charging information (e.g., withoutlimitation, the time to reach a fully charged state) for theircorresponding EVs 400 to the other EV charging circuit breakers 300.Each EV charging circuit breaker 300 will then have the EV charginginformation for all of the EVs 400 being charged with power from thetransformer 100. Each EV charging circuit breaker 300 is then able todetermine the charging priority rank of the EVs 400. Each EV chargingcircuit breaker 300 is also able to determine a threshold rank. Thethreshold rank is the rank which divides which EVs 400 may continuecharging and which should stop charging in order to meet the loadshedding level. For example, EVs 400 having a charging priority rank ator below the threshold rank should stop charging during the period oftime associated with load shedding. Since each EV charging circuitbreaker 300 may determine the charging priority rank of it correspondingEV 400 and the threshold rank, each EV charging circuit breaker 300 isable to determine whether it should stop charging its corresponding EV400 during the period of time associated with load shedding. If an EVcharging circuit breaker 300 determines that it should stop charging itscorresponding EV 400 during the period of time associated with loadshedding, it may control itself to stop charging the corresponding EV400 during the period of time.

A central controller is not needed to implement the load sheddingalgorithm. However, it will be appreciated by those having ordinaryskill in the art that a central controller may determine the chargingpriority ranks of EVs 400 and control selected EV charging circuitbreakers 300 to turn off charging during the time period associated withload shedding. Similarly, one of the EV charging circuit breakers 300may be designated as a master and serve as the central controllerwithout departing from the scope of the disclosed concept.

In addition to EVs 400, the electrical distribution system 1 may providepower to other devices such as the HVAC system 410, the water heater420, or any other electric device that draws power. For example, eachload center 200 may distribute power to a residence and all electricdevices that use power in that residence. Various circuit breakers inaddition to the EV charging circuit breakers 300 may be provided in theload centers 200 to provide power to electric devices other than the EVs400.

In some embodiments, the load centers 10 may receive power fromrenewable power sources such as, without limitation, the photovoltaicsystem 20 in addition to power received from the transformer 100. The EVcharging circuit breakers 300 may be configured to prioritize usingpower provided by the renewable power sources over the power providedfrom the utility 10 via the transformer 100. That is, if power isavailable from the renewable power source, the EV charging circuitbreaker 300 will use that power to charge the EV 400.

Referring to FIG. 2, a schematic diagram of an EV charging circuitbreaker 300 according to an example embodiment of the disclosed conceptis shown. The EV charging circuit breaker 300 includes severalcomponents, some of which will be described in more detail herein. TheEV charging circuit breaker 300 is electrically connected between apower source (e.g., without limitation, the utility 10, the photovoltaicsystem 20, or another power source) and its corresponding EV 400. The EVcharging circuit breaker 300 is configured to receive power from thepower source via LINE (Lin) and NEUTRAL (Nout) input terminals and toprovide power to the corresponding EV 400 via LINE (Lout) and NEUTRAL(Nout) output terminals. Signaling and communication may also be sent orreceived via a pilot (p) terminal.

The EV charging circuit breaker 300 includes circuit protectioncircuitry 302. The circuit protection circuitry 302 may include firstseparable contacts 304, an operating mechanism 306, and a trip unit 308.The circuit protection circuitry 302 is structured to detect a fault(e.g., without limitation, overcurrent, arc fault, etc.) by monitoringpower flowing between the power source and the EV 400 and trip open thefirst separable contacts 304 in response to detecting the fault. Forexample, in some embodiments, the circuit protection circuitry 302includes the trip unit 308 structured to receive information on thepower flowing between the power source and the EV 400 via one or moresensors (not shown). Based on the received information, the trip unit308 determines whether a fault is detected. In response to detecting afault, the trip unit 308 outputs a trip signal to the operatingmechanism 306. The operating mechanism 306 is structured to open andclose the first separable contacts 304. In response to receiving thetrip signal, the operating mechanism 306 is structured to trip open thefirst separable contacts 304. Although an example of circuit protectioncircuitry 302 has been described herein, it will be appreciated by thosehaving ordinary skill in the art that other types of circuit protectioncircuitry may be employed without departing from the scope of thedisclosed concept. For example and without limitation, in someembodiments the circuit protection circuitry 302 may include athermal/magnetic trip mechanism structured to trip open in response topredetermined fault conditions.

The EV charging circuit breaker 300 may also include metering circuitry310 which is capable of metering power passing through the EV chargingcircuit breaker 300. The metering circuitry 310 may include one or moresensors such as a current sensor 312 used to sense the current of powerflowing through the EV charging circuit breaker 300. The meteringcircuitry 310 may also include other type of sensors such as, withoutlimitation, a voltage sensor (not shown).

The EV charging circuit breaker 300 may further include controlcircuitry 314. The control circuitry 314 may include second separablecontacts 316. The second separable contacts 316 may be controlled toopen or close regardless of whether a fault condition exists. Forexample and without limitation, the second separable contacts 316 may beopened to cause the EV charging circuit breaker 300 to stop charging thecorresponding EV 400. The control circuitry may include a secondoperating mechanism (not shown) such as a solenoid to open and close thesecond separable contacts 316.

The EV charging circuit breaker 300 may additionally include groundfault detection circuitry 318. The ground fault detection circuitry 318may include a ground fault coil 320 and a ground fault detector 322. Theground fault detection circuitry 318 is structured to sense currentflowing through line and neutral conductors in the EV charging circuitbreaker 300 and the ground fault detector 322 is structured to determinewhether a ground fault is present based on the detected currents. Inresponse to detecting a ground fault, the ground fault detector mayoutput a ground fault signal. The EV charging circuit breaker 300 maycause the first or second separable contacts 304,316 is response to theground fault being detected.

A communication interface 326 may also be provided in the EV chargingcircuit breaker 300. The communication interface 326 providescommunication functionality which allows the EV charging circuit breaker300 to communicate with other devices such as other EV charging circuitbreakers 300, the transformer 100, or other devices. The communicationinterface 326 may provide functionality for wired or wirelesscommunication using any suitable wired or wireless communicationprotocols.

A processing unit 324 is also provided in the EV charging circuitbreaker 324. The processing unit 324 may include a processor and anassociated memory. The processor may be, for example and withoutlimitation, a microprocessor, a microcontroller, or some other suitableprocessing device or circuitry. The memory may be any of one or more ofa variety of types of internal and/or external storage media such as,without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the likethat provide a storage register, i.e., a machine readable medium, fordata storage such as in the fashion of an internal storage area of acomputer, and can be volatile memory or nonvolatile memory. In someembodiments of the disclosed concept, one or more routines that may beexecuted by the processor may be stored in the memory of the processingunit 324.

The processing unit 324 may control the various components in the EVcharging circuit breaker 300. Routines stored in the processing unit 324which, when executed by the processing unit 324, cause the EV chargingcircuit breaker 300 to implement various functionality. In someembodiments, the processing unit 324 may store a routine which, whenexecuted, causes the EV charging circuit breaker 300 to determine therandom delay time and to stop charging its corresponding EV 400 untilthe random delay time after the end of the load peak period passes.Also, in some embodiments, the processing unit 324 may store a routinewhich, when executed, causes the EV charging circuit breaker 300 toimplement the previously described load shedding algorithm.

The EV charging circuit breaker 300 further includes electric vehiclecharging circuitry 328. The EV charging circuitry 328 allows the EVcharging circuit breaker 300 to provide communication and/or controlfunctionality associated with charging the corresponding EV 400. In someexample embodiments of the disclosed concept, the EV charging circuitry328 may generate a pilot signal that provides for signaling andcommunication for use by the corresponding EV 400. Some EV chargingstandards, such as the SAE J1772 and IEC 61851 standards, use a pilotsignal to provide signaling and communication with an EV. For example,an SAE J1772 compliant pilot signal is a pulse width modulated signalwhose voltage level indicates a charging status (e.g., standby, vehicledetected, ready, with ventilation, no power, error) and whose duty cycleindicates an ampere capacity of the charging equipment. In someembodiments, the EV charging circuitry 328 may generate a pilot signalin accordance with the SAE J1772 or the IEC 61851 standards.

FIG. 3 is a flowchart for a constrained randomized delay method forcharging EVs. The method of FIG. 3 may be implemented in an EV chargingcircuit breaker 300. For example, the method may be implemented when aroutine stored in the processing unit 324 is executed by the processingunit 324. At 600, the estimated charging time for the corresponding EV400 to reach the fully charged state is estimated by the EV chargingcircuit breaker 300. For example, the EV charging circuit breaker 300may use historical charge pattern data and the amount of time the EV 400has currently been charging to estimate the charging time to reach thefully charged state.

At 610, the maximum delay time is determined. For example, the EVcharging circuit breaker 300 may store start and end times associatedwith a predetermined charging window. The start and end times may be,for example, the end of a peak load period and a predetermined time inthe morning. The EV charging circuit breaker 300 may determine themaximum delay time as the difference between the length of thepredetermined charging window and the estimated amount of time requiredfor the EV 400 to reach the fully charged state.

At 620, a random delay time is selected by the EV charging circuitbreaker 300. The random delay time is an amount of time that is lessthan or equal to the maximum delay time. The random delay time israndomly selected with the constraint that it must be less than or equalto the maximum delay time. Any suitable method for selecting a randomvalue may be employed to select the random delay time.

At 630, charging of the EV 400 is turned off until the random delay timepasses from the start time of the predetermined charging window. Even ifthe EV 400 is plugged into the EV charging circuit breaker 300, the EVcharging circuit breaker 300 will not start charging the EV 400 untilthe random delay time has passed after the start time of thepredetermined charging window. For example, if the start time of thepredetermined charging window is 8:00 PM and the random delay time is1.5 hours, the EV charging circuit breaker 300 will begin charging theEV 400 at 9:30 PM. Since the random delay time is randomly selected, therandom delay time may be a different amount of time the next day thatthe EV 400 is plugged into the EV charging circuit breaker 300 forcharging.

In some example embodiments of the disclosed concept, the EV chargingcircuit breaker 300 may also be configured to turn off charging itscorresponding EV 400 for a predetermined peak load period before thepredetermined charging window. For example, the predetermined peak loadperiod may be immediately before the predetermined charging period sothe EV charging circuit breaker 300 will not be charging the EV 400 atthe beginning of the predetermined charging window. However, it iscontemplated that the EV charging circuit breaker 300 may charge the EV400 in the period immediately preceding the predetermined chargingwindow. In this case, the EV charging circuit breaker 300 may first stopcharging the EV 400, and then wait the random delay time from the startof the predetermined charging window before starting to charge the EV400 again.

It is contemplated that the method of FIG. 3 may be implemented inmultiple EV charging circuit breakers 300 simultaneously. Since each EVcharging circuit breaker 300 individually selects its own random delaytime, it is unlikely that multiple EV charging circuit breakers 300would begin charging their corresponding EVs 400 simultaneously.Moreover, the EV charging circuit breakers 300 do not need tocommunicate with each other to coordinate when to begin charging theircorresponding EVs 400.

FIG. 4 is a chart of an example of the total load on the transformer 100in the electrical distribution system 1 of FIG. 1 when the method ofFIG. 3 is implemented in the EV charging circuit breakers 300.Additionally, in the example shown in FIG. 4, the EV charging circuitbreakers 300 begin in a state where they are not charging theircorresponding EVs 400 and only begin charging their corresponding EVs400 after their respective random delay times from the start of thepredetermined charging window. In this example, the predeterminedcharging window starts at 7:00 PM.

The example chart shows the total load 702 on the transformer 100. Thebase load 706 (i.e., the load due to non-EV devices) and the EV load 704(i.e., the load due to charging EVs 400) are also shown. An alternatetotal load 708 and an alternate EV load 710 are also shown. Thealternate total load 708 and the alternate EV load 710 are the loadsthat would be imposed on the transformer 100 if the EV charging circuitbreakers 300 were permitted to immediately begin charging theircorresponding EVs 400 when the EVs 400 were plugged in. The alternatetotal load 708 and alternate EV load 710 are based on random plug-intimes having a mean of 5:30 PM and a standard deviation of 1.5 hours.

The chart of FIG. 4, shows a significant improvement in the peak loadimposed on the transformer 100 when the method of FIG. 3 is implementedby the EV charging circuit breakers 300. For example, the peak of thetotal load 702 shows about a 40% increase over the peak of the base load706 due to the EV load 704 when the method of FIG. 3 is implemented bythe EV charging circuit breakers 300. The peak of the alternate totalload 708, on the other hand, shows about a 145% increase over the peakof the base load 706.

FIG. 5 is a chart of an example of the total load on the transformer 100if the EV charging circuit breakers 300 delayed charging until apredetermined time after the start of the predetermined charging windowrather than their respective random delay times. In other words, all EVs400 plugged into their corresponding EV charging circuit breakers 300will begin charging at the same time. In this example, the predeterminedtime is 10:00 PM. The total load 712 and the EV load 714, as well as thepreviously described base load 706, alternate total load 708, andalternate EV load 710, are shown in the chart of FIG. 5. As shown inFIG. 5, starting to charge the EVs 400 at the predetermined time causesthe peak of the total load 712 to increase by about 320% over the peakof the base load 706. Also, as shown in FIG. 5, the EV load 714 is asignificant cause of the higher peak. Thus, delaying charging the EVs400 until a predetermined time, even if the predetermined time is afterthe peak load period, causes an increase in the peak of the total load712 than if the method of constrained randomized delay of FIG. 3 isimplemented in the EV charging circuit breakers 300.

FIG. 6 is a flowchart of a method of load shedding in accordance with anexample embodiment of the disclosed concept. The flowchart illustrates aload shedding algorithm that may be implemented, for example, in one ormore of the EV charging circuit breakers 300 connected to thetransformer 100 in the electrical distribution system 1 shown in FIG. 1.It is not necessary that all of the EV charging circuit breakers 300connected to the transformer 100 implement the load shedding algorithm.Use of the load shedding algorithm may be incentivized, for example, byproviding a customer who chooses to have the load shedding algorithmimplemented in a EV charging circuit breaker 300 at their residence witha discount to their electric bill.

At 800, the load shedding process is initiated. The load shedding may beinitiated at a predetermined time. Alternatively, the load sheddingprocess may be initiated in response to an event. For example, thetransformer 100 may issue a command to initiate the load sheddingprocess when its load exceeds a threshold level. The load sheddingprocess may have an associated load shedding level and a period of time.The load shedding level and period of time may be predetermined andstored in the EV charging circuit breaker 300. In some embodiments, theload shedding level and period of time may not be predetermined. Forexample, the load shedding level may be determined based on the totalload imposed on the transformer 100 and the period of time may lastuntil the total load imposed on the transformer 100 falls below athreshold level. However, it will be appreciated by those havingordinary skill in the art that the load shedding level and period oftime may be based on other variables without departing from the scope ofthe disclosed concept.

At 810, the EV charging circuit breaker 300 estimates the charging timeto reach a fully charged state for its associated EV 400. For example,the EV charging circuit breaker 300 may use historical charge patterndata and the amount of time the EV 400 has currently been charging toestimate the charging time to reach the fully charged state.

At 820, the EV charging circuit breaker 300 transmits the estimatedcharging time for its corresponding EV 400. For example, the EV chargingcircuit breaker 300 may transmit the estimated charging time to reachthe fully charged state for its EV 400 to all of the other EV chargingcircuit breakers 300 that are connected to the transformer 100 and haveimplemented the load shedding algorithm. Any suitable method may be usedto transmit the estimated charging times to all of the other EV chargingcircuit breakers 300. At 830, the EV charging circuit breaker 830receives the estimated charging times from each of the other EV chargingcircuit breakers 300 that are implementing the load shedding algorithm.

At 840, the EV charging circuit breaker 300 ranks the charging priorityof the EVs 400 corresponding to itself and the EV charging circuitbreakers 300 that it received estimated charging times from. The ranksare based on the lengths of the estimated charging times. For example,an EV 400 having a longer estimated charging time will have a highercharging priority rank than an EV 400 with a shorter estimated chargingtime to reach the fully charged state.

At 850, the EV charging circuit breaker 300 determines the thresholdrank. The threshold rank is the rank that divides which EVs 400 cancontinue charging and which EVs 400 should stop charging in order tostop charging the minimal number of EVs 400 while still lowering thetotal load on the transformer 100 by at least the amount of the loadshedding level.

At 860, the EV charging circuit breaker 300 determines whether thecharging priority rank of its corresponding EV 400 is greater than thethreshold rank. If the charging priority rank of the corresponding EV400 is less than or equal to the threshold rank, the EV charging circuitbreaker 300 stops charging its corresponding EV 400 at 870. On the otherhand, if the charging priority rank of the corresponding EV 400 isgreater than the threshold rank, the EV charging circuit breaker 300continues charging it corresponding EV 400 at 880.

It is contemplated that the load shedding algorithm may be implementedin multiple EV charging circuit breakers 300 simultaneously. Theperformance of the load shedding algorithm may be improved by increasingthe number of EV charging circuit breakers 300 that implement itsimultaneously as there will be more corresponding EVs 400 to rank andit may be easier to reduce the total load by the load shedding level.

FIG. 7 is a chart showing an example of an implementation of the loadshedding algorithm in a number of EV charging circuit breakers 300simultaneously. In the example shown in FIG. 7 the period of timeassociated with the load shedding algorithm is 9:00 PM-11:00 PM and theload shedding level is 100 kW. The chart in FIG. 7 illustrates the timeversus the state of charge of a number of EVs 400. For simplicity ofillustration, reference number 900 is used for plots corresponding toEVs 400 that are at or below the threshold rank at the beginning of thetime period associated with load shedding and reference number 950 isused for plots corresponding to EVs 400 that are above the thresholdrank at the beginning of the time period associated with load shedding.As shown in FIG. 7, charging for several EVs 400 (plots labeled withreference number 950) is stopped during the period of time associatedwith load shedding while charging for some EVs 400 (plots labeled withreference number 900) is allowed to continue during the period of timeassociated with load shedding. The result of stopping charging for someEVs 400 during the period of time associated with load shedding is thatthe total load on the transformer 100 is reduced by the load sheddinglevel for that period. Additionally, stopping charging for EVs 400having the lowest charging priority ranks increases the likelihood thatEVs 400 that need more time to charge will not have their chargingstopped during the period of time associated with load shedding.

It is contemplated that in some embodiments the load shedding algorithmmay ensure that EVs 400 will be fully charged by a predetermined time inthe morning. For example, if an EV 400 will not be fully charged by thepredetermined time in the morning if its charging is stopped during theload shedding period of time, the load shedding algorithm may allow theEV 400 to continue charging even if its charging priority rank is at orbelow the threshold rank. However, this scenario is unlikely as an EV400 needing a long time to become fully charged will have a highercharging priority rank and likely would not fall below the thresholdrank.

Although EV charging circuit breakers 300 are disclosed in connectionwith the disclosed concept, it will be appreciated that embodiments ofthe disclosed concept may also be implemented in other types of EVcharging devices without departing from the scope of the disclosedconcept. For example, in some embodiments, the EV charging circuitbreakers 300 may be replaced by EV charging devices that provide similarEV charging functionality as the EV charging circuit breakers 300, butdo not provide circuit protection functionality.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

What is claimed is:
 1. An electric vehicle charging device for use incharging a corresponding electric vehicle electrically connected to theelectric vehicle charging device, the electric vehicle charging devicecomprising: control circuitry structured to selectively allow theelectric vehicle charging device to charge the electric vehicle; acircuit protection unit structured to provide circuit protection betweenthe electric vehicle and a power source, the circuit protection unitincluding first separable contacts electrically connected between theelectric vehicle and the power source and an operating mechanismstructured to trip open the separable contacts in response to a faultbeing detected in power flowing to the electric vehicle, wherein thefault is at least one of an overcurrent fault and an arc fault; and aprocessing unit having a memory with a routine stored therein which,when executed by the processing unit causes the processing unit to:estimate a charging length of time needed for the electric vehicle toreach a fully charged state; determine a maximum delay length of time asa difference between a predetermined length of time and the charginglength of time, wherein the predetermined length of time is defined by apredetermined start time and a predetermined end time; randomly select arandom delay length of time that is less than or equal to the maximumdelay length of time; and control the control circuitry to prevent theelectric vehicle charging device from charging the electric vehicle fora random delay period and to allow the electric vehicle charging deviceto charge the electric vehicle starting when the random delay periodends, wherein the random delay period starts at the predetermined starttime and lasts the random delay length of time.
 2. The electric vehiclecharging device of claim 1, wherein the routine stored in the memory,when executed by the processing unit, further causes the processing unitto: control the control circuitry to prevent the electric vehiclecharging device from charging the electric vehicle for a load peakperiod of time, wherein the load peak period of time begins prior to thepredetermined start time and ends at the predetermined start time. 3.The electric vehicle charging device of claim 1, wherein executing theroutine further causes the processor to: estimate a full charge lengthof time based on historical charge pattern data, wherein the full chargelength of time is the length of time for the electric vehicle to reachthe fully charged state from the time it is electrically connected tothe electric vehicle charging device if the electric vehicle iscontinuously charged; determine a current charge length of time as anamount of time the electric vehicle has been charging since it has beenelectrically connected to the electric vehicle charging device; anddetermine the charging length of time needed for the electric vehicle toreach a fully charged state as the full charge length of time minus thecurrent charge length of time.
 4. The electric vehicle charging deviceof claim 1, wherein the circuit protection unit further comprises: atrip unit structured to receive information on power between a powersource and the electric vehicle and to determine whether the fault isdetected based on the information.
 5. The electric vehicle chargingdevice of claim 4, wherein the trip unit is structured to output a tripsignal to the operating mechanism in response to the fault beingdetected, and wherein the operating mechanism is structured to trip openthe first separable contacts in response to receiving the trip signalfrom the trip unit.
 6. The electric vehicle charging device of claim 1,wherein the circuit protection unit includes a thermal/magnetic tripmechanism.
 7. The electric vehicle charging device of claim 1, whereinthe control circuitry includes second separable contacts, and whereinthe control circuitry is structured to open the second separablecontacts to prevent the electric vehicle charging device from chargingthe electric vehicle.
 8. The electric vehicle charging device of claim1, further comprising: electric vehicle charging circuitry structured togenerate a pilot signal that provides signaling or communication for useby the electric vehicle.
 9. The electric vehicle charging device ofclaim 1, further comprising: a housing structured to house the controlcircuitry, the circuit protection unit, and the processing unit.
 10. Anelectric vehicle charging device for use in charging a correspondingelectric vehicle electrically connected to the electric vehicle chargingdevice, the electric vehicle charging device comprising: controlcircuitry structured to selectively allow the electric vehicle chargingdevice to charge the electric vehicle; a processing unit having a memorywith a routine stored therein which, when executed by the processingunit causes the processing unit to: estimate a charging length of timeneeded for the electric vehicle to reach a fully charged state;determine a maximum delay length of time as a difference between apredetermined length of time and the charging length of time, whereinthe predetermined length of time is defined by a predetermined starttime and a predetermined end time; randomly select a random delay lengthof time that is less than or equal to the maximum delay length of time;and control the control circuitry to prevent the electric vehiclecharging device from charging the electric vehicle for a random delayperiod and to allow the electric vehicle charging device to charge theelectric vehicle starting when the random delay period ends, wherein therandom delay period starts at the predetermined start time and lasts therandom delay length of time; and a housing structured to house thecontrol circuitry and the processing unit.
 11. The electric vehiclecharging device of claim 10, wherein the routine stored in the memory,when executed by the processing unit, further causes the processing unitto: control the control circuitry to prevent the electric vehiclecharging device from charging the electric vehicle for a load peakperiod of time, wherein the load peak period of time begins prior to thepredetermined start time and ends at the predetermined start time. 12.The electric vehicle charging device of claim 10, wherein executing theroutine further causes the processor to: estimate a full charge lengthof time based on historical charge pattern data, wherein the full chargelength of time is the length of time for the electric vehicle to reachthe fully charged state from the time it is electrically connected tothe electric vehicle charging device if the electric vehicle iscontinuously charged; determine a current charge length of time as anamount of time the electric vehicle has been charging since it has beenelectrically connected to the electric vehicle charging device; anddetermine the charging length of time needed for the electric vehicle toreach a fully charged state as the full charge length of time minus thecurrent charge length of time.
 13. The electric vehicle charging deviceof claim 10, further comprising: a circuit protection unit structured toprovide circuit protection between the electric vehicle and a powersource, the circuit protection unit including first separable contactselectrically connected between the electric vehicle and the power sourceand an operating mechanism structured to trip open the separablecontacts in response to a fault being detected in power flowing to theelectric vehicle, wherein the fault is at least one of an overcurrentfault and an arc fault.
 14. The electric vehicle charging device ofclaim 13, wherein the circuit protection unit further comprises: a tripunit structured to receive information on power between a power sourceand the electric vehicle and to determine whether the fault is detectedbased on the information.
 15. The electric vehicle charging device ofclaim 14, wherein the trip unit is structured to output a trip signal tothe operating mechanism in response to the fault being detected, andwherein the operating mechanism is structured to trip open the firstseparable contacts in response to receiving the trip signal from thetrip unit.
 16. The electric vehicle charging device of claim 13, whereinthe circuit protection unit includes a thermal/magnetic trip mechanism.17. The electric vehicle charging device of claim 13, wherein thecontrol circuitry includes second separable contacts, and wherein thecontrol circuitry is structured to open the second separable contacts toprevent the electric vehicle charging device from charging the electricvehicle.
 18. The electric vehicle charging device of claim 10, furthercomprising: electric vehicle charging circuitry structured to generate apilot signal that provides signaling or communication for use by theelectric vehicle.
 19. A system comprising: a transformer structured toreceive power from a utility; at least one load center electricallyconnected to the transformer and structured to receive power from theutility via the transformer, wherein the at least one load centerincludes a first load center including at least one electric vehiclecharging device structured to use power received by the first loadcenter to charge a corresponding electric vehicle electrically connectedto the at least one electric vehicle charging device, wherein the atleast one electric vehicle charging device comprises: control circuitrystructured to selectively allow the electric vehicle charging device tocharge the electric vehicle; a circuit protection unit structured toprovide circuit protection, the circuit protection unit including firstseparable contacts and an operating mechanism structured to trip openthe separable contacts in response to a fault being detected in thepower received by the first load center, wherein the fault is at leastone of an overcurrent fault and an arc fault; and a processing unithaving a memory with a routine stored therein which, when executed bythe processing unit causes the processing unit to: estimate a charginglength of time needed for the electric vehicle to reach a fully chargedstate; determine a maximum delay length of time as a difference betweena predetermined length of time and the charging length of time, whereinthe predetermined length of time is defined by a predetermined starttime and a predetermined end time; randomly select a random delay lengthof time that is less than or equal to the maximum delay length of time;and control the control circuitry to prevent the electric vehiclecharging device from charging the electric vehicle for a random delayperiod and to allow the electric vehicle charging device to charge theelectric vehicle starting when the random delay period ends, wherein therandom delay period starts at the predetermined start time and lasts therandom delay length of time.